While I'm sure that the drug companies would lose a great deal of revenue if all type 2's began low carbing, not all type 2's would be able to discontinue medications simply because of low carbing. Some type 2's have too many burned out beta cells to control by diet alone by the time that they are diagnosed. Nor do I believe that all type 2's would choose low carbing over medications if given an informed choice. Heck...ask any group of doctors how well their patients comply with even the ADA diet, let alone low carb. Type 1's would also continue to require insulin and other medications whether they were low carbing or not, just less of them.
My whole point in the above post is that many would rather take the medications than change their eating habits even knowing that the dietary changes would offer them less complications and better health in the long run. I've run into this myself with people I know at work who would rather continue to take medication because they simply aren't willing to give up the foods that the medication allows them to eat and still maintain some degree of control although I have to admit that I find that whole line of thinking puzzling to say the least. Then again, perhaps it's really no different than people who continue to smoke even though they know the dangers that it presents to their bodies and even after they've been diagnosed with lung cancer or COPD.
I think this applies with any diet that people are "told" to go on. Unless it's their choice, chances are good that they won't be committed to it for the long haul.